1. Field of the Invention
The present invention relates to a vertical-type backlight unit suited for flat display panels, and more particularly, to a vertical-type backlight unit having a plurality of removable lamp module cartridges.
2. Description of the Prior Art
Backlight modules are known as a key component for the liquid crystal displays, which are widely applied to different kinds of products such as digital cameras, notebooks, personal digital assistants (PDAs), mobile phones, vehicle satellite navigation systems, computer monitors, flat panel TVs and so on. Since the liquid crystal displays are passive luminous devices, a back light unit is required for the LCD devices to meet the requirements of night vision and full color imagery. Basically, the back light unit, which is disposed under the display panel, comprises a luminous means and a diffuser for generating light beams and scattering the light beams uniformly to the display panel. According to the position of the luminous means, the back light units are divided into several types, such as the vertical-type back light unit, in which the light source is generated under the display panel, or the edge-type back light unit, in which the light source is projected from the edges. Among all kinds of back light units, since the vertical back light unit generates light beams under the display panel, therefore, the vertical back light units are widely used in large size display panels or those display panels which need high brightness, such as TV sets.
Referring to FIG. 1, it is a cross-sectional view of a vertical back light module 50 according to the prior art. The vertical back light module 50 is disposed under a display panel 12 and comprises a plurality of lamp tubes 14, a diffusing plate 56, and a reflection plate 18. The lamp tubes 14 are arranged in a close chamber 30 defined by the diffusing plate 56 and the subjacent metal reflection plate 18. The reflection plate 18 is utilized for upwardly reflecting the light source generated by the lamp tubes 14 and thereby increase the light use efficiency of the back light module 50. The diffusing plate 56 is employed for scattering the light source to the display panel 12. Typically, the diffusing plate 56 is made of acrylic or propylene carbonate (PC) having a light transmittance of about 50% to 80%. In some cases, a diffusing sheet 20 and an optical film 22 are disposed over the diffusing plate 56. Typically, the diffusing sheet 20, which is made of acrylic or PC, has a higher light transmittance than that of the diffusing plate 56 and has a thickness of about 0.11 mm to 0.15 mm.
However, the above-described prior art vertical backlight unit 50 has a drawback in that it is time-consuming and very inconvenient to change the lamp tubes. When one of the lamp tubes does not function well or becomes out of order, the users have to carefully remove the display panel 12, the diffusing sheet 20, the optical film 22, and then the diffusing plate 56 from the housing with a screw or other like tools to replace it with a new one. Occasionally, some people abandon the whole liquid crystal display device that only has one or two lamp tubes out of order because they don't know how to change the lamp tubes. In light of the foregoing, it becomes apparent that there is a need for an improved vertical backlight unit module that is convenient for the users to change lamp tubes when some of which are out of order.